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Post by Deleted on Jan 15, 2020 23:58:05 GMT
34w is presumably what it says on the label on the back? That’s likely to be the absolute maximum power with full brightness, full volume etc. Normal power consumption is likely to be less But let’s presume its correct. Taking into account inverter efficiency can be done by assuming the voltage is 10v and thus the current is 3.4A. So 3.4Ah for each hour it is on. If it is on 24 hrs a day that would be 81.6Ah. But presuming a more normal 4 hrs a day, that would be 13.6Ah a day. Ok. So tonight I've had it on for 2 hrs, along with my fridge freezer. The bmv says I have used 17.6 amps, and my voltage reading from a separate meter says 12.52. The full charge finished at 8pm. I'm assuming my trojans are on the way out? Out of curiosity, what is the wattage of your fridge freezer? About 60 watts by any chance? [Corrcted myself there] I'll take a couple of the Trojans off your hands if you are chucking them out. They're probably in better nick than my current battery. I'm probably passing you in a couple of weeks.
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Post by Telemachus on Jan 16, 2020 0:05:37 GMT
“3 amps per hour” is a meaningless statement. Why? 1ah is equivalent to 1 amp of current flowing for 1 hour. Yes, 1 amp flowing for 1 hours is obviously 1 ah. You multiply current x hours to get amphours. Amps per hour means amps divided by hours, in the same way that miles per hour is calculated by dividing miles by time. “per” means divided by, and if the divisor is time you get the rate. So amps per hour means the rate of change of current. It would be 3 amps per hour if the current started out at 3A and slowly decreased so that after one hour it was zero. Put another way, with Ah the longer the time, the more Ah is consumed for a given current. With A/h the longer the time the less the value is.
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Post by Telemachus on Jan 16, 2020 0:13:55 GMT
34w is presumably what it says on the label on the back? That’s likely to be the absolute maximum power with full brightness, full volume etc. Normal power consumption is likely to be less But let’s presume its correct. Taking into account inverter efficiency can be done by assuming the voltage is 10v and thus the current is 3.4A. So 3.4Ah for each hour it is on. If it is on 24 hrs a day that would be 81.6Ah. But presuming a more normal 4 hrs a day, that would be 13.6Ah a day. Ok. So tonight I've had it on for 2 hrs, along with my fridge freezer. The bmv says I have used 17.6 amps, and my voltage reading from a separate meter says 12.52. The full charge finished at 8pm. I'm assuming my trojans are on the way out? Fridge freezers are quite thirsty, I’d reckon on 60-70 Ah per day. “... says I have used 17.6 amps” is a meaningless statement so it’s hard to give a sensible answer. But if you want to know the capacity of the bank, wait until the no load rested voltage is around 12.2v and then note how many Ah have come out of the batteries according to the BMV. Double that figure is the capacity. It could be that one cell in one battery is dragging the rest down. Do you notice one battery behaving differently? Warmer, gassing differently, electrolyte of a cell looking different? Possibly, removing one pair might improve things, if a cell in that pair is internally shorting and discharging the rest.
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Post by Deleted on Jan 16, 2020 0:21:55 GMT
No unusual activity in cells, though I did have a look at the plates today, and some had a sort of muddy red discoloration at the top. I'm wondering if that's oxidation.
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Post by Deleted on Jan 16, 2020 0:26:41 GMT
Why? 1ah is equivalent to 1 amp of current flowing for 1 hour. Yes, 1 amp flowing for 1 hours is obviously 1 ah. You multiply current x hours to get amphours. Amps per hour means amps divided by hours, in the same way that miles per hour is calculated by dividing miles by time. “per” means divided by, and if the divisor is time you get the rate. So amps per hour means the rate of change of current. It would be 3 amps per hour if the current started out at 3A and slowly decreased so that after one hour it was zero. Put another way, with Ah the longer the time, the more Ah is consumed for a given current. With A/h the longer the time the less the value is. Hmm...yes, the basic unit for electrical charge is the Coulomb. 1 amp is the equivalent to the flow of 1 Coulomb per second. So an amp hour is equivalent to the flow of 3600 Coulombs per hour.
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Post by Deleted on Jan 16, 2020 0:27:42 GMT
Ok. So tonight I've had it on for 2 hrs, along with my fridge freezer. The bmv says I have used 17.6 amps, and my voltage reading from a separate meter says 12.52. The full charge finished at 8pm. I'm assuming my trojans are on the way out? Out of curiosity, what is the wattage of your fridge freezer? About 60 watts by any chance? [Corrcted myself there] I'll take a couple of the Trojans off your hands if you are chucking them out. They're probably in better nick than my current battery. I'm probably passing you in a couple of weeks. How do you know you will be passing me? I'm moving every couple of days at the moment.
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Post by Deleted on Jan 16, 2020 0:32:28 GMT
Out of curiosity, what is the wattage of your fridge freezer? About 60 watts by any chance? [Corrcted myself there] I'll take a couple of the Trojans off your hands if you are chucking them out. They're probably in better nick than my current battery. I'm probably passing you in a couple of weeks. How do you know you will be passing me? I'm moving every couple of days at the moment. Well you were at the Grove about a week ago so it does depend which way you are going I suppose. MK or London?
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Post by Telemachus on Jan 16, 2020 8:31:07 GMT
Yes, 1 amp flowing for 1 hours is obviously 1 ah. You multiply current x hours to get amphours. Amps per hour means amps divided by hours, in the same way that miles per hour is calculated by dividing miles by time. “per” means divided by, and if the divisor is time you get the rate. So amps per hour means the rate of change of current. It would be 3 amps per hour if the current started out at 3A and slowly decreased so that after one hour it was zero. Put another way, with Ah the longer the time, the more Ah is consumed for a given current. With A/h the longer the time the less the value is. Hmm...yes, the basic unit for electrical charge is the Coulomb. 1 amp is the equivalent to the flow of 1 Coulomb per second. So an amp hour is equivalent to the flow of 3600 Coulombs per hour. First and second sentences correct, third sentence wrong - not dimensionally consistent. As you say, a coulomb is a unit of charge. An Ah is also a unit of charge, so their relationship doesn’t involve time. An Ah is 3600 coulombs. 3600 coulombs per hour is a measure of current. One coulomb per hour is 1/3600A. 3600 coulombs per hour is (1/3600 x 3600) 1 amp.
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Post by Deleted on Jan 16, 2020 9:24:22 GMT
How do you know you will be passing me? I'm moving every couple of days at the moment. Well you were at the Grove about a week ago so it does depend which way you are going I suppose. MK or London? Well I'm roughly 15 miles from grove.
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Post by Deleted on Jan 16, 2020 11:00:43 GMT
Well you were at the Grove about a week ago so it does depend which way you are going I suppose. MK or London? Well I'm roughly 15 miles from grove. Well if you are heading South then we wont be passing you...if that helps... :-)
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Post by Deleted on Jan 16, 2020 11:08:30 GMT
Hmm...yes, the basic unit for electrical charge is the Coulomb. 1 amp is the equivalent to the flow of 1 Coulomb per second. So an amp hour is equivalent to the flow of 3600 Coulombs per hour. First and second sentences correct, third sentence wrong - not dimensionally consistent. As you say, a coulomb is a unit of charge. An Ah is also a unit of charge, so their relationship doesn’t involve time. An Ah is 3600 coulombs. 3600 coulombs per hour is a measure of current. One coulomb per hour is 1/3600A. 3600 coulombs per hour is (1/3600 x 3600) 1 amp. So is an amp hour simply 3600 Coulombs of charge? When people quote the ah rating of a battery they see 105ah meaning that the battery theoretically can 'give up' 105 amps over 1 hour (or 57.5 amps over 2 hours etc). Also ah means amp hour, so time is in the title. Just to add that the specified voltage of a battery is also a factor in how much specified charge a battery can hold. For example a single 6v 210ah battery holds about the same charge as a single 12v 105ah battery.
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Post by Telemachus on Jan 16, 2020 11:30:24 GMT
First and second sentences correct, third sentence wrong - not dimensionally consistent. As you say, a coulomb is a unit of charge. An Ah is also a unit of charge, so their relationship doesn’t involve time. An Ah is 3600 coulombs. 3600 coulombs per hour is a measure of current. One coulomb per hour is 1/3600A. 3600 coulombs per hour is (1/3600 x 3600) 1 amp. So is an amp hour simply 3600 Coulombs of charge? When people quote the ah rating of a battery they see 105ah meaning that the battery theoretically can 'give up' 105 amps over 1 hour (or 57.5 amps over 2 hours etc). Also ah means amp hour, so time is in the title. Yes to the first 2 sentences. Regarding your last sentence, yes time is in the title, multiplied by amps. But amps, as you said earlier, is charge per second. So for Ah we have Charge / time x time (charge divided by time multiplied by time) which is just charge. The confusion arises I think because amps is a rate like miles per hour, but the “per hour” or “per second” bit is implicit in the unit.
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Post by lollygagger on Jan 16, 2020 11:38:34 GMT
so 1A is 1 coulomb/second?
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Post by lollygagger on Jan 16, 2020 11:40:17 GMT
and an Amp HOUR is 1 coulomb per second for an hour so it does need the hour bit.
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Post by Deleted on Jan 16, 2020 11:41:18 GMT
so 1A is 1 coulomb/second? Yes. I was thinking, maybe batteries should be rated in Coulombs not ah... ;-)
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